Borchardt, Roy A. PA-C, PhD
Roy Borchardt is a PA in the department of infectious diseases, infection control, and employee health at the University of Texas M.D. Anderson Cancer Center in Houston, Texas, and department editor of Special Topics in .... The author has indicated no relationships to disclose relating to the content of this article.
ABSTRACT: Viral and Group A beta-hemolytic streptococcal (GAS) pharyngitis have overlapping signs and symptoms, but distinguishing between the two is critical to proper treatment. Antibacterial therapy is appropriate for GAS pharyngitis and may help prevent complications.
Acute pharyngitis, or sore throat, is one of the most common infections encountered in primary care. Most acute pharyngitis is caused by respiratory viruses, but several species of bacteria also cause acute pharyngitis. Among the bacterial species, Group A beta-hemolytic Streptococcus (GAS) is the most common bacterial pathogen. In children, GAS accounts for 15% to 30% of acute pharyngitis and occurs most frequently in children ages 5 to 15 years, primarily during winter and early spring. In adults, GAS accounts for 5% to 10% of acute pharyngitis.1 GAS pharyngitis is typically a self-limiting illness, but can result in suppurative complications, such as peritonsillar abscess or mastoiditis, and non-suppurative complications, such as acute rheumatic fever, rheumatic heart disease, and post-streptococcal glomerulonephritis. These complications largely can be prevented with appropriate antibacterial therapy. Antibacterial treatment also can decrease the duration of symptoms and reduce the rate of transmission. Therefore, distinguishing between viral pharyngitis and GAS pharyngitis is key.2 Unfortunately, the clinical presentations of viral and GAS pharyngitis have overlapping signs and symptoms, such that no single element of the history or physical examination accurately excludes or diagnoses GAS pharyngitis.3 Clinical judgment alone results in an 80% to 95% overestimate of the disease, and consequently, an overprescribing of antibiotics.4
The symptoms of GAS pharyngitis include sudden-onset sore throat, pain with swallowing, and fever. Children may have headache, nausea, vomiting, and abdominal pain. Physical examination reveals erythematous tonsillopharyngeal mucosa with or without exudates, and lymphadenitis with tender and enlarged anterior cervical lymph nodes. Other findings can include erythematous (beefy red) uvula, hard palate petechiae, scarlatiniform rash, and excoriated nares, especially in infants.1 Exposure to GAS within 2 weeks before the onset of symptoms also suggests GAS pharyngitis. These classical clinical presentations are observed in only 20% to 30% of patients with GAS pharyngitis.
The absence of fever and presence of conjunctivitis, cough, coryza, stomatitis, conjunctivitis, diarrhea, hoarseness, and ulcerative oropharyngeal lesions strongly suggest viral pharyngitis. Some patients experience recurrent bouts of GAS pharyngitis shortly after resolution of initial disease. Others may experience a recurrence of pharyngitis symptoms, but may be colonized with GAS of the oropharynx without actual GAS infection, and are actually experiencing viral pharyngitis.2
The gold standard for diagnosing GAS pharyngitis is a positive throat swab culture on sheep-blood agar plate from a patient with suggestive clinical signs and symptoms. A single throat swab culture has high sensitivity (90% to 95%) for detecting GAS. The disadvantage of throat culture is the delay in providing results—an 18- to 24-hour incubation period at 35° to 37° C is needed before results can be determined. Alternatively, the rapid antigen detection testing (RADT), which detects the group-specific cell wall carbohydrate antigen of GAS, can provide results in a matter of minutes. Commercially available RADTs, using enzyme-linked immunosorbent assays or optical immunoassays, or newer DNA probe chemiluminescence assays, have good diagnostic performance with a high degree of specificity (95% or more), but a more variable degree of sensitivity (90% to 99%, depending on the kit used). The older latex agglutination assay RADT kits have sensitivities around 70%.5 The high degree of specificity of these tests minimizes the likelihood of a false-positive result, and provides a strong level of confidence for subsequent therapeutic decision making. Neither throat culture nor RADT can distinguish between acute pharyngitis infection with GAS and an asymptomatic GAS carrier with a viral pharyngitis.2
Recently, the 2002 Infectious Diseases Society of America guidelines on the diagnosis and management of GAS pharyngitis were revised. Unless epidemiological and clinical observations strongly suggest a viral etiology, swab the patient's throat and test for GAS by culture and/or RADT. A positive GAS culture or RADT in a patient with clinical signs and symptoms of acute pharyngitis establishes the diagnosis. A positive RADT does not require a follow-up confirmatory culture. Perform a back-up throat culture on children and adolescents with a negative RADT. A back-up throat culture is not necessary for adults with a negative RADT because the incidence of acute rheumatic fever is low in adults with acute pharyngitis.
Routine testing is not indicated for symptomatic children under age 3 years because the incidence of GAS pharyngitis and acute rheumatic fever is very low in this population. Routine testing should not be performed on asymptomatic household members of patients with GAS pharyngitis. Consider testing for symptomatic children under age 3 years who have an older sibling with GAS infection. Posttreatment follow-up throat culture or RADT is not recommended.6
Current recommendations state that patients with GAS pharyngitis should be treated with an appropriate antibiotic for 10 days. Penicillin or amoxicillin are the preferred antibiotics for patients without penicillin allergies. Oral penicillin V is the drug of choice because it has narrow spectrum of activity, has proven efficacy and safety, and is inexpensive. Amoxicillin is often substituted for young children, because its taste is more palatable.
For adolescents and adults, the penicillin V dose is either 250 mg four times daily or 500 mg twice daily. For children, the dose of penicillin V is 250 mg twice or three times daily. For amoxicillin, the dose is 50 mg/kg body weight once daily up to a maximum of 1,000 mg; alternatively, 25 mg/kg (up to 500 mg maximum) can be given twice daily.
For patients unlikely to comply with a full 10-day course, a one-time dose of intramuscular benzathine penicillin G can be used at a dose of 600,000 units (if the patient weighs less than 27 kg [59.5 lb]) or 1.2 million units (if over 27 kg).6
Patients who are penicillin-allergic and without anaphylactic sensitivity can receive 10 days of a first-generation cephalosporin. Either cephalexin at 20 mg/kg body weight twice daily (up to a maximum of 500 mg per dose), or cefadroxil at 30 mg/kg body weight once daily (up to a maximum of 1 gram) can be used. Patients with penicillin allergy and anaphylactic sensitivity can receive either a 10-day course of clindamycin at 7 mg/kg body weight three times daily (up to a maximum of 300 mg per dose), or clarithromycin at 7.5 mg/kg body weight twice daily (up to a maximum of 300 mg per dose); alternatively, these patients can receive a 5-day course of azithromycin at 12 mg/kg body weight once daily (up to a maximum dose of 500 mg).6
For patients with moderate to severe symptoms and/or high fever associated with GAS pharyngitis, consider adjuvant therapy with an analgesic or antipyretic. Acetaminophen or a nonsteroidal anti-inflammatory drug can be used. Aspirin should not be used in children under age 12 due to its association with the development of Reye syndrome. Corticosteroids are not recommended as adjuvant therapy.6
Despite the recommendations for treatment with a 10-day course of antibiotics, studies in Israel suggest that most children discontinue their antibiotic therapy after 4 to 6 days, corresponding to 1 or 2 days after their fever resolves. There was no increase in incidence of suppurative or non-suppurative complications observed during a 10-year follow-up period.7 A recent analysis of 20 randomized controlled trials, comparing short duration newer oral cephalosporin antibiotics (2 to 6 days) to standard 10-day oral penicillin in children ages 1 to 18 with GAS pharyngitis found comparable efficacy. The short duration treatment had better compliance, but more self-limiting adverse reactions were observed, primarily mild to moderate GI symptoms of vomiting, diarrhea, and abdominal pain. Conclusions on differences in complication rates could not be drawn, because only 3 out of the 20 studies followed patients for sufficient duration to assess the prevalence of complications.8 These results imply that shorter durations of antibiotic therapy may be sufficient, but further studies are needed to assess long-term safety.
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© 2013 American Academy of Physician Assistants.